As Lisa mentioned a few weeks back, a panel convened by the National Academy of Sciences recently concluded that compact, walkable neighborhoods can significantly reduce CO2 emissions from driving. USAToday described the findings this way:
Meeting the growing demand for conveniently located homes in neighborhoods designed to encourage walking could significantly reduce the number of miles Americans drive while giving people more housing choices, a national research panel has concluded.
If you want to fight global warming, one good way could be to live in a more compact neighborhood – with more neighbors and jobs close by, and where mass transit, biking and walking are accessible alternatives to the car.
But at about the same time, Technology Review ran an article summarizing a study that found the exact opposite: “Forget Curbing Suburban Sprawl,” the headline cautioned, “Building denser cities would do little to reduce CO2 emissions.”
Confused? Well, prepare to get even more confused: the Technology Review article was covering the exact same National Academy of Sciences report as USAToday and The Oregonian. Same study, but two completely opposing interpretations. What gives?
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Well, the truth is that you can point to bits and pieces of the report that justify both perspectives.
USA Today and the Oregonian focus on the panel’s review of the academic literature—which shows, quite clearly, that neighborhood design exerts a powerful influence on how much driving we do. Living in a mixed-use neighborhood—with a mixture of single family homes and multi-family housing, with some stores, transit, and other services nearby—might cut the average person’s driving by perhaps a third to a half, compared with car-dependent sprawl. Living in an even more compact urban neighborhood, with lots of stores and jobs within walking distance, might cut per capita driving by a half to two-thirds, or perhaps more.
At the level of an entire metropolis, the effects of compact design can be signficant. The report found that Portland’s metropolitan land use and transportation planning system, in place since the 1970s, has cut city residents’ driving by 17 percent. Just so, residents of the comparatively compact Boston metro area drive a quarter less than do folks in sprawling Atlanta.
And yet the study also notes that land use can’t change overnight. It’s long, slow work to turn a place like Atlanta into a place like Boston. And Portland’s success in reining in sprawl has been hard earned—and even then, the reduction in gasoline use in Portland is comparable to what would be achieved by lifting average vehicle gas mileage from 20 mpg to 23 mpg.
That’s where the Technology Review’s gets its pessimism. At least one panel member went on record saying that changing land use policies was too slow, too difficult, and requires too much intergovernmental coordination, to do much to rein in greenhouse gases.
As I see it, there are at least 5 major reasons why we shouldn’t settle for the more pessimistic view.
1) We should think on the margins: A metro area’s population might grow only a percent or two a year, so the averages don’t budge much year-to-year. But on the margins, encouraging new development in denser areas turns out to be a very effective way of reducing the greenhouse gas emissions from new residents. Over the long haul, it’s the margins that matter, since they control the direction of change.
2) There’s more to emissions than how much we drive: Reductions in driving understate the climate benefits of compact neighborhoods. As this study shows, living in a compact neighborhood doesn’t just reduce how many miles you drive, it also seems to increase the odds that you’ll choose a more fuel efficient car. And compact neighborhoods can also reduce net emissions for heating, cooling, and powering your home.
3) Creating alternatives to sprawl has multiple benefits. Channeling growth into compact neighborhoods can help protect farmland and open space; reduce wasteful spending on public infrastructure; promote health; reduce impervious surface per capita; and so forth. As important as greenhouse gases are, it’s only one reason among many for curbing sprawl.
4) Waiting for the feds is a sucker’s game. Cities and towns that want to take action to protect the climate simply can’t sit back and wait for federal action on, say, boosting auto fuel efficiency. Waiting for the feds is the lazy way out—and given the ever-changing nature of politics, it’s an incredibly risky strategy, since even the most progressive federal policies can change overnight.
5) Over the long haul, even small things matter—a lot. Global warming is a long-term problem, and it requires long-term solutions. Sure, it could take 50 years or more for changes in urban form to take a major bite out of US emissions. But if the developed world is going to make the massive emissions cuts that are going to be necessary, we’re going to have to employ every single tool at our disposal.
In the end, then, I see the fatalistic view of land use—essentially, that changing land use is just too much hard—as not merely unhelpful, but unethical. Rather than bemoan how hard it is to make progress, I’d rather buckle down and get to work.
Not to mention that by saving farmland, the ’emmissions cost’ of food can be reduced by making locally grown produce an option.
The additional impact of energy efficiency in buildings due to compact neighborhoods needs to be stressed. By various measures, buildings contribute 40% to 50% of U.S. greenhouse gas emissions. So making buildings more efficient can have a much bigger impact than reducing driving, though compact neighborhoods help with both.The actual design of the buildings matters, though. Housing units should share walls and floors (apartments, condos, townhouses) rather than just be separate single-family houses with tiny yards between them. The same applies to retail and commercial spaces. This makes heating and cooling more efficient, and also saves on materials.Housing units should also be smaller, which again reduces energy use. In summary, if we just take giant suburban McMansions and cram them together onto smaller lots we will not achieve most of the benefits of compact development. We actually have to increase population density by reducing unit size and building attached units.
Has a calculation been done that considers the CO2 emissions cost of building in urban environments – MUCH more concrete? Suburban residential building also accounts for some sequestration of carbon – in all of those 2x4s and plywood.
I wonder about this, and the two competing interpretations. For one it’s not just CO2 in terms of environmental impact. But I really see the impact of compact development and a strong transit system in Washington, DC, observationally in terms of traffic on the streets.DC at the core has a dense grid street network, subway and surface transit, and walkable neighborhoods convenient to job centers.Except for key routes into and out of the city, there is relatively little traffic, all in all, of course, except during commuting periods.I say this as a bicylist, and judging by whether or not I can ride through intersections on red lights, only only only if there isn’t oncoming traffic (or a long distance between cars so that traversing the street is safe).I can ride through many major intersections through red lights, even during rush hours.That’s true IN THE CITY, which has the most compact land development pattern in the region. It is not true in the suburbs. And DC’s resident commuting times compare favorably to national averages, even though typically a trip by walking, public transportation, or bicycling, except if very short, is longer than a comparable automobile trip.You don’t see the same level of impact in Seattle (or Portland, despite the hype) maybe, because those cities are much more sprawling compared to DC, seemingly maybe, because the street network is somewhat different, particularly in Seattle. Note that DC’s transportation demand management programming is pathetic, while Portland and to some extent Seattle plan transportation much much much better. (Try finding info on public transportation at DC area airports, and compare that to how it’s handled in Portland or Seattle, and that is but one example. Compare transit info in the PSU library or the UW student bookstore to any college campus in the DC region. There are no comparable examples. Etc.)Yet DC’s mode shift is 2x better than Portland’s (city to city, maybe not within the region). And DC’s mode shift is 2/3 better than Seattle.Of course, a real _subway_ _network_ makes a huge difference. So does having a strong job center downtown.
Clark, great article. I agree that despite how long term this problem is to change, all the better reason we should be starting now. Our very well of settling down breeds excess and waste. Like you said, there is more to think about than just what comes out of a tailpipe. Wider distances between homes and towns means more power lines (which bleed power), more sewer pipe, more gas and water lines; all of which cost money to install and money to maintain. Less compact development also breeds parking lots—a waste of land coated with asphalt (far from environmentally friendly) and the creation of heat islands. I would also add one reason to your list. Let us not forget that our built environment is not “done” yet. We are constantly adding more housing to the country which means we should be switching now so at the very least, the bleeding stops. All new development should be centered around existing towns and cities while focusing on infill and proximity to transit. Most often the actions that make the most difference are those that challenge the social norms of our lifestyle. They will be a challenge, but they need to be done.
I think the main driver of sprawl is the mortgage underwriting guidelines that barely take into account energy use of a home (your large suburban detached home uses about 2-3 times the energy of a moderately sized attached home) and completely ignores transportation costs due to automobile ownership. The mortgage interest deduction and high leverage makes home ownership (in most times) a great investment, so there is a huuuuge incentive for people to buy, and “driving until you qualify” still works. You can look at total cost of ownership, including transportation costs and you will have a great picture of where foreclosures are happening now. Since we are re-writing the mortgage rules as we speak, we might as well re-structure them to acknowledge the true risks and costs of home ownership. If we do this properly, then a major incentive to sprawl is removed, and we can level the playing field for infill development, promote transit oriented communities, and work towards climate stabilization. All without spending a nickel on convincing NIMBY-ists. We just shift the underlying demand model and people will demand more infill housing because that’s all they can afford.